Tiptop Buchla 207t + 296t: Newest Members of the 200t Family

Buchla 200 Mixer + Programmable Spectral Processor Reimagined for Eurorack

Perfect Circuit · 05/11/23

Tiptop Audio made a splash at Superbooth 2021 with the introduction of their Buchla 200t lineup: Eurorack modules developed with the blessing of Buchla USA, aimed at recreating the sound and workflow of Don Buchla's iconic 200 Series instruments in a more accessible, affordable form factor.

The modules are all based on original 200 Series circuitry, adapted largely for the purpose of accommodating Eurorack-specific panel and voltage level requirements. As such, they do (obviously) differ from Don Buchla's 200 Series: the layouts have changed, panel dimensions are smaller, and in some cases, new features are added or (simple) features on the originals are excluded. But, the core functionality and sound of these modules are quite similar to the original modules—so if you're looking for a taste of the workflow and sound of these rare instruments, the 200t series is a remarkably popular option.

As of May of 2023, Tiptop has produced and shipped all six of the originally proposed core 200t modules: the 258t Dual Oscillator, 281t Quad Function Generator, 257t Dual Voltage Processor, 245t Sequential Voltage Source, 266t Source of Uncertainty, and most recently, the 292t Quad Lopass Gate. With all of these core modules out the door, it only makes sense that it's time to introduce the next steps...and now, we know what they are: the 207t Mixer/Preamplifier, and the 296t Programmable Spectral Processor.

Let's take a look at each of these modules, breaking down the unique roles they'll serve in the developing 200t lineup.

207t Mixer + Preamplifier

Tiptop's 207t is a somewhat chonky-looking reimagining of Don Buchla's 207 Mixer/Preamplifier, a staple part of several 1970s Buchla systems. Chonkiness aside, it promises to be a quite useful addition to many Eurorack and 200t-centric setups: 207t is a stereo mixer with channel mutes, monitoring facilities, and an integrated preamp for boosting external instruments and microphones.

The 207t includes a six-channel mixer with a variety of signal routing options. Toward the bottom of each channel, you'll notice switches labeled "Mon" and "Prog"; these allow you to route the channel's signal to the Monitor and L&R Signal Outputs (aka Program Outputs), respectively. The signal sent to the monitor outputs is always full-volume and summed to mono—useful for simple monitoring applications, rudimentary mixing, or the creation of a pseudo-aux-send.

When a channel has the Prog switch set to the upward position, the channel is sent to the Signal Outputs, with loudness defined by the Level Adjustment slider, and panning determined by the Channel Assignment knobs. The middle four channels feature manual pan control, while the first and sixth channels offer voltage control of panning. These outer channels are hard-panned when no CV is applied; the first channel is hard panned to the left program output, and the sixth channel to the right. By applying a positive control voltage at the corresponding CV inputs, the signal can be panned toward the opposite direction.

The preamp section features a 1/4" input and multiple gain settings, with a continuous amplification control; it offers enough gain for use with external line level instruments, electric guitars, or even dynamic microphones. Finally, the "Expansion In" is a stereo input which sums to the left and right main outputs—great for chaining multiple 207t modules, or creating a stereo effect return, or simply for adding in another stereo source at the final output.

Though its functionality is quite simple, the 207t will no doubt be the glue that holds many a 200t system together.

296t Programmable Spectral Processor

The other new module in the 200t lineup is the 296t Programmable Spectral Processor, modeled after the rare Buchla 296. As with the 207t and other 200t offerings, fitting all of the controls in a 3U rack space led to a considerably altered panel layout; however, all of the front-panel features of the original are still represented on this modern re-creation.

The 296t is a sixteen-channel fixed filter bank with a number of distinct features. The module features three audio inputs at the bottom right, labeled Even, All, and Odd. Patching to the All input sends your signal to all sixteen filters; patching to Even sends it through only the even-numbered filters (0–E), and patching to the Odd input sends your signal through the odd-numbered filters (1–F). From there, understanding the 296t requires taking a closer look at all of the outputs sections.

The most prominent output section is located directly above the array of sliders. The sixteen audio outputs provide direct output from each filter band. The sixteen color-coded blue and violet outputs produce envelope follower signals corresponding to the loudness of each individual filter band, with a decay time determined by the Env Decay Time switch. This is a great way of using any audio source to produce a wide range of modulation signals. On the top right of the module, the Comb Filter Outputs produce a sum of all of the odd and even bands, respectively.

The Attenuator Outputs produce sums of the odd, even, and all filters based on the levels indicated by the per-filter level control sliders. You can think of this section as acting somewhat like a graphic equalizer, where each band can be turned down to absolute silence, or boosted by up to ~6dB for a subtle resonant peak. The rest of the module is unaffected by the level sliders.

The final output section is perhaps the most interesting. The Programmed Outputs produce a sum of the odd, even, and all filter bands; but rather than relying on the level control sliders for their individual volume control, they use a combination of several CV sources. The first is the Program Control section, which allows you to define a voltage-controllable "width" and "frequency"—in a sense, "scanning" the filter bank to produce effects similar to a variable-width bandpass filter. The Programmed Spectrum Transfer section section allows you to internally connect the envelope follower outputs from the odd bands to the even bands' CV inputs, or vice versa—creating a crude-yet-effect eight-band vocoder. Lastly, the Programmed Output section also respects the front-panel "Local Program Inputs"—direct inputs for voltage control of each individual filter's signal level. This is great for creating alien soundscapes, sequenced multi-band rhythms, and much more.

Long story short? If you need an enormous sampling of ways to create spectral motion and complex filtering arrangements, the 296t promises to be an effective and relatively affordable way to approximate the sound of one of the most rare and flexible filter banks in history.

Inspired by Timeless Designs

Tiptop's line of 200t modules continues to be a source of inspiration to many. The 207t fills a very obvious gap in Tiptop's original 200t lineup, and we expect it'll be a welcome addition to many a rack. The 296t, on the other hand, is arguably the most ambitious of the series so far, aiming to recreate Don Buchla's most complex modular designs.

It will never be possible to completely authentically re-create Don Buchla's work in Eurorack format—if only because the literal real estate means that panel layouts need to be changed, and because the realities of mass production mean that components need to be more uniformly selected for use across an entire product line. So, no, strictly speaking, these aren't exact replicas of Buchla modules, internal circuitry notwithstanding. However, based on our experience with the currently-available line of modules? They're a lot of fun; they're affordable; and they sound excellent. They provide a healthy taste of the sound and workflow of vintage Buchla instruments, they've provided a ton of inspiration for tons of musicians, and they're bringing more focus onto the work of one of the most brilliant electronic instrument designers of all time—albeit in a roundabout way. For those who are looking for a colorful and unique way of approaching sound manipulation and interaction in their Eurorack system, they'll no doubt prove to be quite welcome.